The 12ga would be less likely to pass through, and more likely to cause large amounts of internal damage. On the other hand the 20ga is more likely to pass though and less likely to cause a great deal of internal damage.
I think you have it backwards..
Mac
Sorry Mac...
It looks like you are letting your personal experiences cloud your thoughts concerning the ballistics discussion that was occurring.
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As I understand it, the original discussion centered around the ft/lbs of energy. Very simply the author wanted to know the likely effect of two similar scenarios.
#1). a heavy blunt object moving relatively slowly...
#2). a sharper lighter object moving faster...
In both cases the projectiles are carrying identical amounts of energy...what are the potential effects of each projectile?
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MAC,
Which projectile do you think will penetrate deeper, and which do think will leave a wider path of destruction?
Remember, they both have the same amount of energy to expend, it can only be spent vertically,(penetration) or horizontally, (damage).
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(put another way..going back to the actual original question)
"But what I really want to know is if there's a substantial difference in the damage done between a 260 gr. and a 438 gr slug when the energy of the two are virtually the same? "
The question centers around the wound cavity. Which bullet is likely to leave to leave a longer, thinner wound channel, and which bullet is more likely to leave a shorter, wider channel?
JC